Figure 3(a) Atomic naming scheme for the antidiarrhetic loperamide hydrochloride (Brüning et al., 2012). H atom labels were omitted for clarity as they carry the name of their parent atoms. (b) Three-dimensional deformation electron density (0.1 e Å−3 isosurface) from fast Fourier transform with MoleCoolQt that helps to validate the assignment of the local atomic coordinate systems on the click of the mouse.